Objective The objective of this study is to use computational fluid dynamics (CFD) numerical simulation method to compare geometric and hemodynamic parameters between the cases suffering from primary dissection and the normal cases, providing evidence for the pathogenesis and prediction of Type-B aortic dissection. Methods The study includes six primary Type-B dissection cases scanned by CT and six normal cases applied to MRI. Then patient-specific three-dimensional models of aorta were established through image segmentation and 3-D reconstruction. The pre-Type-B dissection aortas were constructed by applying the scaling algorithm to shrink the dissection. We compared the differences between morphological parameters and hemodynamic parameters of the two groups. Results Compared with the normal cases, the area of the descending aorta increases dramatically in the dissection group (892.03±263.78mm2 vs 523.67±64.10mm2, p=0.036); significant drop in the angle of the left subclavian artery occurred(66.62±20.11vs100.40±15.35, p=0.036); the tortuosity of the aorta also has an obvious increase(0.37±0.07vs0.21±0.51, p=0.011). If somewhere in the aorta shows higher average wall shear stress (AWSS); the velocity is not uniform and the value of the Oscillating Shear Index (OSI) is higher, Type-B aortic dissection is more likely to occur in this area. Conclusions Obvious changes in anatomical (larger area of the descending aorta; smaller angle of the left subclavian artery;more tortuous aorta)and flow related parameters(higher average wall shear stress; unsteady flow; higer Oscillating Shear Index) for the aorta subjected to dissection, providing guidance for the clinical practice.